Liquid crystal displays are formed by a liquid crystal layer overlying a plurality of conductive electrodes, each defining a pixel of the image displayed by the overlying liquid crystal layer. A particular pixel or a portion of the liquid crystal layer may be rendered nonreflective by supplying an electric current to the corresponding underlying electrode. The individual electrode defining each pixel may be addressed by row and column by means of an underlying metal oxide semiconductor (MOS) integrated circuit formed monolithically with the metal electrodes and the liquid crystal layer.
A fundamental problem in this type of device is that the MOS integrated circuit has a very rough top surface over which the metal electrodes are formed by reason of the planar non-uniformity between various ones of the thin film layers forming the MOS integrated circuit, as is well known in the art. The resulting rough surface of the metal electrode deposited over the MOS integrated circuit reduces the amount of the incident light reflected through the liquid crystal. This in turn reduces the contrast between non-reflecting pixels (in which the corresponding electrode supplies an electric current) and reflecting pixels in a liquid crystal layer. Typically, a 20 to 1 contrast ratio is achieved in such devices, the contrast ratio being limited by the rough contour of the top metal surface over which the liquid crystal layer is formed. Thus, it has seemed that the necessity for controlling a liquid crystal display using an underlying MOS integrated circuit unavoidably limits the contrast ratio which may be achieved with liquid crystal displays using MOS integrated circuits.